1. Field of the Invention
The present invention relates to a developing device usable for an image forming apparatus such as an electrophotographic copying machine or a printer, and more particularly to improvements in a developing device, a process cartridge using this developing device, and an image forming apparatus, in which the developing device comprises a developing unit for developing an electrostatic latent image on an image carrier into a visual image, and an auxiliary developing unit connected in communication with the developing unit to supplement the development for the developing unit.
2. Background Art
The conventional image forming apparatus of electrophotographic method normally adopts a system in which an electrostatic latent image formed on an image carrier such as a photosensitive drum is developed with the toner by a developing device (into a visible image), and a toner image is transferred onto a transfer medium such as the paper or an intermediate transfer member by a transfer device, while the residual toner on the image carrier is withdrawn by a cleaning device.
And the developing device 500 has a developing unit 510 for developing the image with a developer composed of a toner and a carrier, and additionally a developer refill unit 520 for refilling the developer with the consumption of developer used in the developing unit 510 to extend the life of this developing unit 510 as shown in FIG. 24 or 25 has already been offered (refer to JP-A-2001-305861, JP-A-10-239970 and JP-A-11-44997).
In the conventional developing device of this type as described in JP-A-2001-305861, the developing unit 510 has a development housing 511 opposed to an image carrier 501 such as a photosensitive drum, in which a developer storage chamber 512 for storing the developer G composed of the toner and the carrier is provided within the development housing 511, a developing roll 513 is disposed in a portion facing an opening of the developing housing 511, and the agitating carrying augers 514 and 515 for agitating and carrying the developer G are disposed within the developer storage chamber 512, as shown in FIG. 24.
On the other hand, the developer refill unit 520 has a refill container 521 for storing the developer G composed of the toner and the carrier, in which the refill container 521 and the development housing 511 are communicated through a communication duct 522 to refill the developer G within the refill container 521 into the developer storage chamber 512 by causing the developer G to fall due to its dead load onto the developer G stored within the developer storage chamber 512.
In FIG. 24, the developer refill unit 520 has a withdrawal container 530 that can withdraw the developer G deteriorated in the developer storage chamber 512, in which the withdrawal container 530 and the development housing 511 are communicated through a communication duct 531.
Also, in the developing device as described in JP-A-10-239970 and JP-A-11-44997, the developing unit 510 is substantially the same as described in JP-A-2001-305861, except that the developer refill unit 520 has a refill housing 541 with a part of the development housing 511 for the developing unit 510 as a housing bulkhead 550, a developer refill chamber 542 storing the refill developer is provided within this refill housing 541, an agitator 543 for agitating and carrying the developer is disposed within the developer refill chamber 542, and a developer refill mechanism and a developer withdrawal mechanism are provided on the side of the developing unit 510 in the developer refill chamber 542, as shown in FIG. 25A.
Herein, the developer refill mechanism is provided with a developer refill passage 545 on a passage bulkhead 544, in which a refill auger 546 is disposed within the developer refill passage 545, and a supply port 547 is opened in the housing bulkhead 550, as shown in FIGS. 25A and 25B. This supply port 547 is provided above the axial center of an agitating carrying auger 515, preferably above the surface position of the developer in a portion where the agitating carrying auger 515 is disposed, to supply the developer smoothly without being subjected to a pressure of the developer G from the developer storage chamber 512.
On the other hand, the developer withdrawal mechanism is provided with a developer withdrawal passage 555 on the passage bulkhead 554, in which a withdrawal auger 556 is disposed within the developer withdrawal passage 555, and a withdrawal port 557 is opened in the housing bulkhead 550, as shown in FIG. 25C. This withdrawal port 557 is provided below the axial center of the agitating carrying auger 515 to increase the ability of withdrawing the developer from the developer storage chamber 512.
However, in the developing device (having the developer refill unit 520) as described in JP-A-2001-305861, because of a structure in which the developing unit 510 and the developer refill unit 520 are communicated through the connection duct 522, the apparatus constitution is enlarged only by a set space of the connection duct 522, and it is difficult to meet the demand of miniaturization easily.
In this respect, in the developing device as described in JP-A-10-239970 and JP-A-11-44997, the developing unit 510 and the developer refill unit 520 are adjacently disposed via the housing bulkhead 550, and the developer refill mechanism or the developer withdrawal mechanism is disposed in the portion along the housing bulkhead 550 in the developer refill chamber 542, whereby it may be possible to attempt the miniaturization of the developing device.
However, since the developing device as described in JP-A-10-239970 and JP-A-11-44997 adopts a structure in which the developer refill passage 545 or the developer withdrawal passage 556 is secured in a part of the area within the developer refill chamber 542, and the refill auger 546 and the withdrawal auger 556 are disposed in the passages 545 and 555, there is an anxiety of obstructing the transportation of the developer as the capacity space of the developer refill chamber 542 is not only uselessly invaded but also the area to which no transportation power by the agitator 543 is exerted occurs in the developer refill chamber 542.
Such a technical problem also arises even if the auxiliary developing units such as the refill unit for refilling only the toner or carrier and the withdrawal unit for withdrawing the deteriorated developer are provided.